We are going to have to isolate our variables. If it is in a sunny location or an area with temp stratifications I would predict top. But without those…wouldn’t the increase in volatile gases near the top insulate it or increase pressure from off gassing more? Therefore the bottom will dry first?

I can’t remember who it was who coined the term (I have the feeling it was Von Neumann, because Feynman mentions this in his biography), but it’s perfect for a physicist to say: “you’re a spherical asshole, because you look like an asshole from every direction and orientation.”